The present invention relates to a method and an apparatus for extracting a three-dimensional shape of an object based on a two-dimensional image displayed on a screen, and to a memory product recording a computer program of the extracting process.
In recent years, with development of multimedia, a processing which handles image taken by a camera is increasing. As one of such processing, there is a processing for extracting a three-dimensional shape of an object from a two-dimensional image of the object displayed on a screen. As such an extracting method of the three-dimensional shape, a method for applying a three-dimensional model (a first conventional example) and a method for designating a three-dimensional axis (a.second conventional example) are known.
In the first conventional example, a three-dimensional shaped model (basic model) such as a cube, a column and a sphere is prepared as an original form, a projective image of the corresponding basic model and an actual picture image of the object are displayed side by side on the screen, both the images are visually compared to designate a relative position, and a three-dimensional shape of the object is extracted by rotating the basic model or by correcting the basic model to change its size.
Further, in the second conventional example, three-dimensional X, Y and Z axes are designated, two-dimensional coordinates of an actual picture image of the object on the screen is converted into three-dimensional coordinates designated using measured focal length, thereby extracting a three-dimensional shape of the object.
In the first conventional example, the correction of the basic model depends on judgement of an operator, and there is a problem that a skilled technique of the operator is required to extract an accurate three-dimensional shape. Further, in the second conventional example, it is necessary to estimate the three-dimensional coordinate system, to retrieve corresponding points, and to conduct the coordinate conversion of the retrieved points and therefore, there is a problem that it takes a long time for processing. Under such an circumstance, development of easy shape extracting method of a three-dimensional object having a relatively simple shape is desired. Further, in any of these conventional examples, measurement of a focal length of an actual picture image which is indispensable to the extracting processing of a three-dimensional shape can not be conducted at the same time, and there is a problem that the focal length must be measured by another technique.
An object of the present invention is to provide three-dimensional shape extracting method and apparatus capable of extremely easily extracting a three-dimensional shape of an object without applying processing of a basic model, retrieving processing of the corresponding points and a skilled technique, by inputting a contour of a surface and geometrical information of the surface of an image of the object, and to provide a computer memory product recording a program for causing a computer to execute the extracting processing.
Another object of the invention is to provide three-dimensional shape extracting method and apparatus capable of simultaneously calculating the focal length in a process of the extracting processing of the three-dimensional shape.
According to the present invention, a contour of one surface of an object displayed on a screen as a two-dimensional image and geometrical information of the surface (such as a square, a hexagon and a circle) are input, and based on the input contour and geometrical information of the surface, a normal vector with respect to a surface of the object in the three-dimensional system and three-dimensional coordinates of one point on the surface are obtained, and one surface of the object in the three-dimensional system is extracted by these obtained parameters. Then, the extracted surface is defined as a bottom surface to determine its height, thereby extracting a three-dimensional shape of the object.
In this manner, according to the present invention, a three-dimensional shape of an.object of columnar shape such as a cube, a hexagonal shape, a column can easily be extracted in a short time only by inputting the contour of a surface and geometrical information of the surface. Further, when the normal vector is obtained, the focal length is also calculated and thus, the focal length information can simultaneously be obtained without using another special technique.